An Influenza A/H1N1/2009 Hemagglutinin Vaccine Produced in Escherichia Coli

The A/H1N1/2009 influenza pandemic made evident the need for faster and higher-yield methods for the production of influenza vaccines. Platforms based on virus culture in mammalian or insect cells are currently under investigation. Alternatively, expression of fragments of the hemagglutinin (HA) protein in prokaryotic systems can potentially be the most efficacious strategy for the manufacture of large quantities of influenza vaccine in a short period of time. Despite experimental evidence on the immunogenic potential of HA protein constructs expressed in bacteria, it is still generally accepted that glycosylation should be a requirement for vaccine efficacy. We expressed the globular HA receptor binding domain, referred to here as HA63-286-RBD, of the influenza A/H1N1/2009 virus in Escherichia coli using a simple, robust and scalable process. The recombinant protein was refolded and purified from the insoluble fraction of the cellular lysate. X-ray structural studies confirm that the protein refolds to closely resemble the original structure of the globular region of native HA protein. Recombinant HA63-286RBD binds specifically to serum antibodies from influenza A/H1N1/2009 patients. Moreover, HA63-286RBD was found to be immunogenic and have protective activity in the ferret model. Our findings demonstrate that glycosylation is not a mandatory requirement for influenza vaccine efficacy.